1. Field of the Invention
This invention pertains to cooling or heat dissipating devices (e.g., thermal transfer devices) such as heat sinks and thermal exchangers, and particularly to devices which accomplish thermal transfer by a circulating fluid.
2. Related Art And Other Considerations
Various types of equipment create or release heat during operation. In some cases the heat can be injurious to the equipment or its environment (e.g., other equipment or components in proximity to the heat-generating or heat-releasing equipment). Accordingly, attempts have been made in some such cases to cool the equipment and/or its environs. Common cooling techniques include circulation of a cooling fluid around or near the source of heat. For example, fans have been used to blow cooling air around a heat-generating component of a system. Alternatively, heat pipes or other types of heat sinks have been placed in contact or nearby the heat source for the purpose of dissipating the heat using, e.g., circulating air.
Among the types of equipment prone to heat generation/release are some electronic components, such as microprocessors, for example. As microprocessor manufacturers are running the microprocessor chips at higher and higher frequencies in order to obtain maximum performance, the chips can build up enough heat to cause failures. In fact, the heat can become so great in many chips that conventional means of cooling (e.g., fans and heat pipes) are not sufficiently effective.
In view of the inadequacy of conventional cooling techniques, fluid cooling of heat generating/releasing components (e.g., electronic chips) is gaining momentum. For example, for cooling purposes a fluid is pumped through a heat sink in contact with the chip die to pick up heat from the chip die. The fluid is then pumped to a heat exchanger for cooling the fluid before the fluid is routed back to the heat sink to pick up and remove more heat.
Some fluid-accommodating heat sinks employ microchannel technology. That is, the heat sinks have “microchannels” through which the cooling fluid travels as it is pumped. The microchannels are very small channels formed in or on a heat sink surface, or the chip die. The heat sink surface with the microchannels may be flush with or otherwise in contact with a surface of a device to be cooled (e.g., chip die).
Despite their proven potential for handling high heat fluxes, microchannel-based heat sinks have not found widespread commercial use, possibly due to the very high pressure drops encountered in the microchannels. High pressure drops necessitate the use of relatively large pumps with significant power requirements, noise, reliability issues, and associated costs.
Moreover, there can be a problem if bubbles form in microchannel-type heat sinks. When a bubble forms in a microchannel of a heat sink, the bubble tends not to exit the channel. Instead, the bubble remains essentially stationary in the microchannel. Since the remaining bubble occludes the cooling fluid flow, a hot spot may develop in or on the device being cooled. If the hot spot grows significantly, the device being cooled may fail.
What is needed, therefore, and an object of this invention, is an efficient and effective thermal transfer device.